Add UserChange data to TransitionRequestInfo

To allow shell to handle the transition request and apply the desktop
activation changes for the current and new user.

Flag: com.android.window.flags.apply_desk_activation_on_user_switch
Bug: 430988310
Test: switch users, check transition request has user change data
Change-Id: Ifb9a3f2d3ada8cb338edbbc2c13d00a16ca27757